Estudo da resistência à corrosão a baixa e alta temperatura de revestimentos PVD depositados em uma superliga de níquel

Abstract

Corrosion problems and failure mechanisms in many components used in oil refineries, such as Hot Gas Expanders, are the subjected of study. The cause of failure of these parts is mainly due to material degradation because it is inserted in a corrosive atmosphere, due to significant sulfur concentrations and other oxidizing agents, also due to the working temperatures of the equipment, which range from 650 to 760° C. Several types of coatings are found in literature that are feasible under the conditions of the equipment, in order to mitigate the effects of corrosion at both high and room temperature. Thus, the present study aimed to evaluate the behavior of thin coatings deposited by the technique of physical vapor deposition (PVD) against corrosion phenomena at both high and room temperature, as a component in the aggressive environment where they are applied. The results strategy to improve the performance of coated of electrochemical corrosion tests showed that the three proposed coatings have the ability to protect the substrate in the following order of protection: TiAlN, CrN, AlCrN, with AlCrN being the most protective. However, at elevated temperatures CrN coatings were fully consumed and the substrate was attacked, while TiAlN and AlCrN coatings were not fully consumed and AlCrN coatings had the lowest corrosion rate values, and based on X-ray diffraction (XRD) results along with scanning electron microscopy (SEM) analysis aided by dispersive energy spectroscopy (EDS) analysis showed that AlCrN coating was the one with the lowest oxidation levels. Based on the obtained results, it is possible to see that the AlCrN PVD coatings appeared as the best alternative to the corrosion phenomena, at high and low temperatures, under the analyzed conditions.